Synthesis and Characterization of Mixed-Ligand Cyclopentadienyl–Pyrazolylborate Complexes of Ruthenium

Amy M. McNaii, David C. Boyd, Kent R Mann

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Neutral compounds of Ru(II) that contain a cyclopentadienyl and a pyrazolylborate ligand were synthesized from [CpRu(CH3CN)3]PF6 and [Cp*Ru(CH3CN)3]PF6 (Cp = η5-cyclopentadienyl; Cp*- = η5-pentamethylcyclopentadienyl). [CpRu(HBpz3)], [CpRuHB(3, 5-Me2pz)3], [CpRuBpz4], and [Cp*Ru(HBpz3)] were characterized spectroscopically. An X-ray crystallographic study of [CpRu(HBpz3)] was completed. CpRu(HBpz3) crystallizes in the P21/m space group with Z = 2, V = 749.8 Å3, a = 9.0854 (4) Å, b = 10.074 (4) Å, c = 8.195 (2) Å, and (3 = 91.50 (3)°. Full-matrix least-squares refinement (112 variables, 2290 reflections) converged to give R and Rw values of 0.043 and 0.052, respectively. The structure consists of discrete (η5-Cp)Ru(HBpz3) units with Ru-C bonds of 2.153 (3) Å and Ru-N bonds of 2.128 (3) Å. Electrochemical measurements for the series of compounds were carried out for comparison with ferrocene and ruthenocene. The compounds exhibit a quasi-reversible, one-electron oxidation that falls in the range 0.145–0.463 V vs. Ag/AgCl. Oxidation of CpRuHB(3,5-Me2pz)3 with AgPF6 allowed the isolation of [CpRuHB(3,5-Me2pz)3]PF6. The thermal reactivity of these compounds allowed the synthesis of the new complexes [CpRuHB(3,5-Me2pz)3(CO)], [CpRuBpz4(CO)], and [Cp2Ru2(CO)2Bpz4]PF6 that exhibit bidentate coordination of pyrazolylborate ligands to ruthenium. While the CpRu pyrazolylborate complexes are formally similar to ruthenocene, the replacement of cyclopentadienyl with a pyrazolylborate ligand significantly alters the chemistry of these new compounds.

Original languageEnglish (US)
Pages (from-to)303-310
Number of pages8
Issue number2
StatePublished - Jan 1 1986

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